Embodiments of the invention are directed to the stabilization of the wavelength of the pump energy while pumping a laser gain medium.
High power laser systems have a broad range of applications throughout the scientific, industrial and medical fields. Laser systems generally include a pump module, a gain medium and a laser resonator. The pump module includes laser diodes or bars that generate pump energy. The gain medium absorbs the pump energy and emits laser light responsive to the absorbed energy. The laser resonator, in some designs, operates to generate a harmonic of the laser light.
The gain medium is generally tuned to absorb pump energy having a wavelength that is within a specified operating band. Thus, the wavelength of the pump energy must be carefully controlled to ensure proper operation of the laser system.
Pumping a yttrium-aluminum-garnet crystal (YAG) rod with neodymium atoms (i.e., a Nd:YAG gain medium) using pump energy having a wavelength of 885 nm has become a desirable pumping scheme due to its natural efficiency gains that can save on cost and electrical/cooling requirements. However, the operating wavelength band of the Nd:YAG gain medium around the 885 nm wavelength is very narrow. Unfortunately, Small changes in the wavelength of the pump energy can cause rapid decreases in the absorption efficiency of the gain medium. Moreover, the wavelength shift in the pump energy away from the narrow operating bandwidth of the Nd:YAG gain medium around 885 nm can also destabilize the wavelength of the pump energy causing it to further deviate from the operating wavelength range of the gain medium.
One option for stabilizing the wavelength of the pump energy is to use a Variable Bragg Grating (VBG) to stabilize the wavelength of the pump energy. However, VBG's are expensive and reduce the efficiency of the pump energy to laser conversion.